1. Field of the Invention
This invention relates to a thermoplastic elastomer composition which is rich in flexibility and excellent in balance of oil resistance, low-temperature resistance and resistance to permeation of Freon gas (air conditioning refrigerant) and the like, particularly to a thermoplastic elastomer suitable for hose materials.
2. Description of Prior Art
As a refrigerant for air-conditioner in automobiles, FREON gas R-12 (CCl.sub.2 F.sub.2) has heretofore been generally used. However, recently, it has been clarified that FREON gas R-12 breaks the ozonosphere in the upper atmosphere and regulation of use of FREON gas R-12 is being internationally strengthened.
As a countermeasure, therefor, the change of the refrigerant from FREON gas R-12 to FREON gas R-22 (CHClF.sub.2) is in progress. However, FREON gas R-22 has a greater permeability to hose materials consisting of elastomers than FREON gas R-12 and hence conventional vulcanized rubber materials consisting essentially of a nitrile rubber used for FREON gas R-12 are insufficient in resistance to permeation of FREON gas R-22.
Therefore, use of a metal tube for FREON gas R-22 is taken into consideration; however, this has such problems that noise is made by vibration during the running of a car and the degree of freedom of piping layout in a bonnet is reduced.
Also, the use of resin hoses consisting essentially of nylon is under consideration; however, there are problems similar to those in the case of use of a metal tube. Therefore, materials having excellent resistance to permeation of FREON gas R-22 have been desired.